Support offset option for pyocd deployments
Some tests need to deploy a base file, boot and test, then deploy a second file whilst leaving the first file in place, boot and test, then potentially deploy a third file which overwrites the earlier app and boot, test that. Allow an option in the deploy block of pyocd support to specify the offset. Pass this number down to the relevant option in pyocd-flashtool. Ensure that deploy boot test deploy boot test mechanisms work for pyocd devices.
Migrated from https://projects.linaro.org/browse/LAVA-1055